How many volts in the 94 M104 Waste Spark system?
 

Just wondering what the coil is putting out. I could swear I saw a spark jumping 1 inch from the end of the plug wire (no plug connected) to the valve cover metal today when checking a cylinder for spark (a helper unplugged one of the plug boots while running).

He was brave... but careful too! His other job is at the hardware store fixing lawnmowers so I guess it was sort of a Briggs and Stratton diagnosis moment for him. He didn't get shocked.....


But I'm wondering... what is the voltage on that. I've heard that it's like 30000 volts to jump an inch.... so I'm guessing it's pretty high!

I don't think I've heard of people getting killed (or wounded) by car ignition coils but still... a 1" spark is pretty impressive... I know I wouldn't enjoy the shock.

There are reports of deaths due to ignition shocks. I personally have been zapped by a modern ignition, and it's damn painful.
Creating large gaps for modern ignition systems to fire across can damage electronic components or lead to the spark coming out of unexpected places. Be carefull.

Mercedes warns of damage potential from cranking/running the car without spark-plugs connected (ignition module damage).

On an open wire with no spark plug 30,000 used to be the voltage,now 50,000 is not uncommon.But a coil will only put out what it needs,no more no less.
What is strange on wastespark ,coilpack type ignition is that they are a/c current ,not d/c as a person may think.
Rich

I don't think that's correct. There is a circuit of current created by a collapsing magnetic field, just as in a single spark. That circuit is DC.

I know it sounds strange and found it hard to believe myself.
This is info i got from some of my smog classes.

Standard coil spark starts in coil goes through plug wire ,jumps plug gap,into frame and back to battery.(simple explanation)
Waste spark ignition goes coil,plug wire,across gap through engine block,jumps gap backwards(?)on the other plug in its pair ,through plug ,then wire on back to coil.never goes back to battery.The spark can start at either plug and and go in any direction.This is why its called a/c current,and waste spark.
Was hard to understand and may not have explained it as well as the book,but thats what we where taught.
So closed circuit,fires both plugs,but not at same time and travels in either direction.
Hope did not confuse,class was 2 or 4 years ago
Rich

Each spark is DC, but true that the direction / polarity is different at each plug.

No confusion here. I am well versed in automotive electronics. The current path is in one direction only even though it goes through one plug in a different direction. It is a true DC circuit.

back to the battery?
 

no...that's not right...not even close

Chas H
 

that is absolutely the goofiest description of an automotive ignition circuit system I have EVER heard...who told you this? AC? No....it's all DC, now it's called Capacitive Discharge Ingnition (CDI), but it's DC based.... and there is no way that any measurable charge from the ingition ever goes back to the battery itself...no way.....

Technically, the electron flow is back to the battery.

Nope the ignition is a circuit. There is no flow back to the battery.
Here a very rough sketch I made for a similar discussion on another forum. The current travels in a circle, hence the name circuit.

There is no condenser in the ignition circuit?

Any ignition circuit that I have ever touched in the past has had a condenser in parallel with the primary coil. The breakdown of the field causes a reverse EMF (i.e., voltage) which charges the capacitor. Then, true to form, the current reverses and the process repeats - a few times.

If you've ever seen an o-scope hooked to an ignition circuit, you would never again claim that the circuit was DC. It is an AC spark. The first half-wave is the strongest, yes, but it's still AC.

This is true of non-waste spark systems. The secondary coil is connected to the spark plug at one end, and the battery + coil connection on the other.

This is not true of non-waste spark systems. The basics are the same for both. Voltage flowing through the primary windings of the coil creates a magnetic field. When this voltage is abruptly interupted, the magnetic field collapses and induces a much higher voltage in the secondary windings. This is the spark plug voltage and it is a circuit that flows through the coil, the spark plug(s) the engine and back to the coil. It does not flow to or through the battery.
Here's a schematic to help.
http://www.sentex.net/~mwandel/cannon/sparky.html

Condenser haven't been used since points went away. There may be small condensers in the igniter circuit, but you won't see any discrete condensers hanging about.
The current in a spark plug circuit does not reverse. Does the voltage on your oscilliscope ever drop below the zero line?

The positive side is broken? Well, I've never seen that one, but I will admit that it could exist. On any system that I have seen with an external coil (where you can actually discern the connections), there was no ground connection at the ignition coil. The high-tension current went through the battery, which won't affect anything given its extremely low impedance.

As for the condenser, I didn't specifically say "external" or "discrete" condenser. I imagine that there's a condenser in there.

I do know how well a points system runs with a bad condenser, as I've had a few go bad on me over the years.

The points typically ground the primary side of the coil. This is how it's been done forever.

Right. That means when the points are open, the only path between the secondary side and ground is through the battery. But 12V one way or the other isn't going to mean much to a secondary ignition circuit.

Fakes:

http://stixpix.com/t%2022.html

http://www.highperformancepontiac.com/tech/hppp_0612_pontiac_ignition_systems/photo_06.html

http://www.mainlineauto.com.au/support/downloads/ca9000/training/IgnitionSystems.pdf

I can't find any online images of an actual scope. But this is what they look like.

Wrong. When the points open the flow of current, which does come from the battery, through the primary windings stops. This causes the magnetic field created by that current to collapse. This induces a secondary current in the seconary windings. This is what makes the spark. The voltage causing the spark does not flow to or through the battery. Study the schematic I recently posted again, 'cause class for ignition systems 101 is over.

The schematic that you posted matches no ignition system that I've seen. Certainly not a points system. You did agree that the points switched the negative lead. Take a coil and an ohm meter and you'll see that there is no internal connection to the ground. The secondary current needs a complete circuit to function, and the circuit is completed through the battery to the ground.

Whoops, that schematic is indeed incorrect.

Here's one that is correct.

That's almost right. It shows a box between the condenser and ground. If that's the ballast, it's in the wrong place. It's also my understanding that the common point is usually the + connection and not the points connection. This can be verified with an ohm meter.

When those points open, the ringing occurs between the primary and condenser (as in any LC circuit). That causes an alternating magnetic field in the core, thus the AC at the plug wire.